The invention relates to earth structures, certain components for use in earth structures and to methods of constructing earth structures.
It is known from EP-A-0 318 243 to provide an earth structure frictionally stabilised by a plurality of elongate stabilising elements in the form of strips extending rearwardly from a facing of the structure into an earth mass. The earth is stabilised throughout the mass by frictional engagement with the strips, thereby enabling the earth mass to behave as an elastic material with greatly improved resistance to failure. The facing of the known structure consists of a series of rows of xe2x80x9cCxe2x80x9d shaped mesh facing panels arranged one above another. The panels in each row are supported by laterally spaced support straps. These are also xe2x80x9cCxe2x80x9d shaped, each having an upright front portion in front of the panels and relatively short upper and lower rearwardly extending portions. These upper and lower portions are connected to an earth stabilising strip. Thus the forward end of each stabilising strip is located between a rearwardly extending upper portion at the top of a support strap in one row and a rearwardly extending lower portion at the bottom of a support strap in the row above. A bolt passes through the upper and lower rearwardly extending portions and the stabilising strip to form a secure connection. The support straps are thus only able to support the facing panels in the desired upright condition when they are themselves bolted to an earth stabilising strip.
WO 95/00712 discloses connectors which attach to facing panels at two separated points and which have a common rear portion for attachment to stabilising strips as described above. Once constructed, this system is a successful one. However, the construction process is not as straightforward as it might be, since the facing panels need to be initially supported by temporary stays.
There are disclosed in EP-A-0 197 000 and DE-U-8 326 632, approximately xe2x80x98Lxe2x80x99 shaped facing panels which may be placed on the ground without extra support. They do however suffer from the disadvantage that they need to be bent specially to the required form. This is difficult and time consuming to carry out on site and if carried out away from the site the resulting cumbersome shape of the facing panels results in high transportation costs.
According to one aspect of the present invention there is provided an earth structure comprising a plurality of facing panels, a stabilised earth mass behind the facing panels and a plurality of supports for supporting the facing panels, said supports having rearwardly located portions and being able to rest on their rearwardly extending portions to support the facing panels during construction.
According to another aspect of the present invention there is provided a support for supporting a facing panel for stabilised earth, the support having a rearwardly located portion and being able to rest on the rearwardly located portion to support the facing panel during construction.
The advantage of using such supports to support the facing panels is that construction is much simplified. The supports can simply rest on their rearwardly located portions (i.e. portions of the supports which are located rearwardly of the facing panels) to support the facing panels, which is convenient and useful at the stage when the facing panels are positioned during construction.
According to another aspect of the present invention there is provided a method of constructing an earth structure, comprising providing a stabilised earth mass behind a facing panel, and providing a support for supporting the facing panel, the support having a rearwardly located portion, wherein the support and the facing panel are positioned with the support resting on its rearwardly located portion to support the facing panel.
In a preferred construction method, a second facing panel and a second support are positioned above the first-mentioned facing panel and support, and the first-mentioned facing panel is backfilled with earth before the rearwardly located portion of the second support is placed on said earth. This simplifies construction, in that backfilling of the first facing panel takes place before the second support is positioned, so that the second support need not obstruct the backfilling procedure.
The supports may be provided separately of earth stabilising means in the earth mass. The separately provided supports are preferably connected to the earth stabilising means, by a bolted or other connection.
According to a preferred embodiment the supports comprise connectors between the facing panels and separate earth stabilising means. Such connectors are preferably relatively small and light in comparison to the facing panels and are therefore easy to transport to a construction site, compared to the xe2x80x98Lxe2x80x99 shaped facing panels of EP-A-0 197 000 and DE-U-8 326 632.
A connector may be attached to an earth stabilising means before being attached to a facing panel. Preferably, however, the connector and the facing panel are connected together first, and then they can be properly positioned before the earth stabilising means is attached.
The stabilising means to be attached to the connector may take various forms, such as those disclosed in WO 95/00712.
Rather than having connectors provided separately of the earth stabilising means, in an alternative form of the invention the supports may themselves comprise earth stabilising means. Thus the supports may comprise forward end portions of the earth stabilising means. Such an arrangement eliminates the need for a connection (e.g. a bolted connection) between a separate connector and an earth stabilising means, and is advantageous over systems having xe2x80x98Lxe2x80x99 shaped panels since the earth stabilising means can be relatively narrow.
Preferably each support has at least two laterally spaced rearwardly located portions. By having laterally spaced rearwardly located portions, the support means can itself be relatively stable against lateral movement during construction, and can thus give improved support for the facing panel. The laterally spaced rearwardly located portions are preferably interconnected in a manner maintaining their relative lateral positions. Such interconnection can be achieved for example by a single member e.g. a bar which extends both rearwardly and laterally (being for example U- or V-shaped), or by a pair of rearwardly extending and laterally spaced members, e.g. a pair of bars which are interconnected by at least one cross-member e.g. a cross-bar.
Each support preferably has an upwardly extending portion extending up a respective facing panel. In order to minimise the size of the support, the upwardly extending portion preferably extends only partly up a facing panel which it supports, for example about half way up.
A support may have a single upwardly extending portion to provide the required support. Preferably however each support has at least two laterally spaced upwardly extending portions. This can impart greater stability to the facing panel whilst the earth structure is being constructed, particularly if it is a relatively flexible mesh panel. It also helps to distribute the load from the earth stabilisation during use.
In one preferred embodiment the upwardly extending portion is connected at an upper end thereof to a rearwardly located portion to form substantially an inverted xe2x80x98Vxe2x80x99 shape. It is a preferred feature of this embodiment that the upwardly extending portion and rearwardly located portion are both engaged with earth stabilising means, to provide attachment thereto.
A preferred feature is that each upwardly extending portion extends from a respective rearwardly located portion. In the case of a connector, each such rearwardly located portion may be connected to a respective discrete earth stabilising means, for example an earth stabilising strip. In a preferred embodiment, however, the rearwardly located portions converge towards the rear of the connector. An earth stabilising means, such as a strip, may then be attached at the common rear point. In the case of the support itself comprising the earth stabilising means, an upwardly extending portion may extend from each edge of the earth stabilising means, for example a ladder shaped strip. Even if the edges of the earth stabilising means are substantially parallel, they could diverge towards the end providing the upwardly extending portions, to increase stability.
If the supports comprise forward end portions of earth stabilising means, the upwardly extending portion could have the same construction as the rest of the earth stabilising means, e.g. by bending one end of a flat earth stabilising member. This has the advantage that a continuous length of earth stabilising material can be made, cut into appropriate lengths and the upwardly extending portions formed. An example of this is a ladder shaped strip having cross-bars both along its earth stabilising length and on its upwardly extending portion. An alternative construction, however, could have the cross-bars omitted from the upwardly extending portion, which may assist connection to a facing panel.
In a particularly preferred embodiment the earth stabilising means comprises a ladder strip having one end bent to form an upwardly extending portion which engages with a mesh facing panel. The width of the ladder strip is chosen to be less than the vertical spacing of the facing panel mesh to allow the upwardly extending portion to pass through the facing panel and to interlock therewith. By arranging the horizontal bars of the upwardly extending portion to be just above those of the mesh facing panel, extra protection against relative slippage between them is achieved.
The ability of the support of the invention to support a facing panel may be advantageous when using sheet metal or concrete facing panels. However, it is usually possible for such panels to be supported during construction by previously installed panels, obviating the need in most cases for a support with a rearwardly located portion. The advantages of the present invention arise particularly when the facing panels are mesh facing panels. These have the advantage of being light in weight and relatively inexpensive.
An upwardly extending portion of a support may be attached to a facing panel by any suitable means, for example by wire ties or the like. Preferably, the upwardly extending portion interlocks with a facing panel by passing through the plane of the panel in opposite directions at two or more vertically separated points. For example, an upwardly extending portion may pass through a panel from behind, extend vertically along the front of the panel some way, pass back through the panel to the rear, and then extend vertically along the rear of the panel some way. This arrangement ensures that no significant rearward rotational movement of the facing panel about the upward portion of the connector is possible, thereby supporting the facing panel during construction. If the facing panel slopes to the rear, for example, then the support member need only be able to restrain rearward rotation when the panel is being initially positioned. Additional restraint, against forward rotation, may be achieved by using wire ties or the like, or by passing the upwardly extending portion through the plane of the facing more than twice.
If mesh facing panels are used, the upwardly extending portion may simply pass through the openings in the mesh, i.e. between the grid wires.
To resist forward movement against pressure from the earth mass during backfilling of the facing panels, there are preferably provided anchor members connected between the facing panels and the support members. In the embodiment described above in which the upwardly extending portion is connected to the rearwardly located portion at an upper end thereof, such an anchor member could be comprised by the rearwardly located portion. Since the facing panels are supported by the support members during construction, they are preferably flat to facilitate transport and storage and also to obviate the need to bend mesh panels if these are used. This reduces expense.
A support may serve to interconnect vertically adjacent facing panels, for example, in the case of mesh facing panels, by being attached to two horizontal bars of vertically adjacent panels. Preferably, a support is attached to a lower portion of a facing panel and the facing panel lower portion is disposed forwardly of an upper portion of a facing panel below. Earth pressure developed at this upper portion is then transmitted, at least partly, to the lower portion of the panel above and then to the support. It is thus not necessary for the support to be attached directly to the lower panel, with the advantage that during earth settlement the upper panel and support can move downwardly by a large distance relative to the lower panel without causing it to bulge.